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/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 19. March 2015
* $Revision: V.1.4.5
*
* Project: CMSIS DSP Library
* Title: arm_biquad_cascade_df1_q15.c
*
* Description: Processing function for the
* Q15 Biquad cascade DirectFormI(DF1) filter.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* - Neither the name of ARM LIMITED nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @addtogroup BiquadCascadeDF1
* @{
*/
/**
* @brief Processing function for the Q15 Biquad cascade filter.
* @param[in] *S points to an instance of the Q15 Biquad cascade structure.
* @param[in] *pSrc points to the block of input data.
* @param[out] *pDst points to the location where the output result is written.
* @param[in] blockSize number of samples to process per call.
* @return none.
*
*
* <b>Scaling and Overflow Behavior:</b>
* \par
* The function is implemented using a 64-bit internal accumulator.
* Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
* The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
* There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
* The accumulator is then shifted by <code>postShift</code> bits to truncate the result to 1.15 format by discarding the low 16 bits.
* Finally, the result is saturated to 1.15 format.
*
* \par
* Refer to the function <code>arm_biquad_cascade_df1_fast_q15()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
*/
void arm_biquad_cascade_df1_q15(
const arm_biquad_casd_df1_inst_q15 * S,
q15_t * pSrc,
q15_t * pDst,
uint32_t blockSize)
{
#ifndef ARM_MATH_CM0_FAMILY
/* Run the below code for Cortex-M4 and Cortex-M3 */
q15_t *pIn = pSrc; /* Source pointer */
q15_t *pOut = pDst; /* Destination pointer */
q31_t in; /* Temporary variable to hold input value */
q31_t out; /* Temporary variable to hold output value */
q31_t b0; /* Temporary variable to hold bo value */
q31_t b1, a1; /* Filter coefficients */
q31_t state_in, state_out; /* Filter state variables */
q31_t acc_l, acc_h;
q63_t acc; /* Accumulator */
int32_t lShift = (15 - (int32_t) S->postShift); /* Post shift */
q15_t *pState = S->pState; /* State pointer */
q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
uint32_t sample, stage = (uint32_t) S->numStages; /* Stage loop counter */
int32_t uShift = (32 - lShift);
do
{
/* Read the b0 and 0 coefficients using SIMD */
b0 = *__SIMD32(pCoeffs)++;
/* Read the b1 and b2 coefficients using SIMD */
b1 = *__SIMD32(pCoeffs)++;
/* Read the a1 and a2 coefficients using SIMD */
a1 = *__SIMD32(pCoeffs)++;
/* Read the input state values from the state buffer: x[n-1], x[n-2] */
state_in = *__SIMD32(pState)++;
/* Read the output state values from the state buffer: y[n-1], y[n-2] */
state_out = *__SIMD32(pState)--;
/* Apply loop unrolling and compute 2 output values simultaneously. */
/* The variable acc hold output values that are being computed:
*
* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
*/
sample = blockSize >> 1u;
/* First part of the processing with loop unrolling. Compute 2 outputs at a time.
** a second loop below computes the remaining 1 sample. */
while(sample > 0u)
{
/* Read the input */
in = *__SIMD32(pIn)++;
/* out = b0 * x[n] + 0 * 0 */
out = __SMUAD(b0, in);
/* acc += b1 * x[n-1] + b2 * x[n-2] + out */
acc = __SMLALD(b1, state_in, out);
/* acc += a1 * y[n-1] + a2 * y[n-2] */
acc = __SMLALD(a1, state_out, acc);
/* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
/* Calc lower part of acc */
acc_l = acc & 0xffffffff;
/* Calc upper part of acc */
acc_h = (acc >> 32) & 0xffffffff;
/* Apply shift for lower part of acc and upper part of acc */
out = (uint32_t) acc_l >> lShift | acc_h << uShift;
out = __SSAT(out, 16);
/* Every time after the output is computed state should be updated. */
/* The states should be updated as: */
/* Xn2 = Xn1 */
/* Xn1 = Xn */
/* Yn2 = Yn1 */
/* Yn1 = acc */
/* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
/* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
#ifndef ARM_MATH_BIG_ENDIAN
state_in = __PKHBT(in, state_in, 16);
state_out = __PKHBT(out, state_out, 16);
#else
state_in = __PKHBT(state_in >> 16, (in >> 16), 16);
state_out = __PKHBT(state_out >> 16, (out), 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* out = b0 * x[n] + 0 * 0 */
out = __SMUADX(b0, in);
/* acc += b1 * x[n-1] + b2 * x[n-2] + out */
acc = __SMLALD(b1, state_in, out);
/* acc += a1 * y[n-1] + a2 * y[n-2] */
acc = __SMLALD(a1, state_out, acc);
/* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
/* Calc lower part of acc */
acc_l = acc & 0xffffffff;
/* Calc upper part of acc */
acc_h = (acc >> 32) & 0xffffffff;
/* Apply shift for lower part of acc and upper part of acc */
out = (uint32_t) acc_l >> lShift | acc_h << uShift;
out = __SSAT(out, 16);
/* Store the output in the destination buffer. */
#ifndef ARM_MATH_BIG_ENDIAN
*__SIMD32(pOut)++ = __PKHBT(state_out, out, 16);
#else
*__SIMD32(pOut)++ = __PKHBT(out, state_out >> 16, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Every time after the output is computed state should be updated. */
/* The states should be updated as: */
/* Xn2 = Xn1 */
/* Xn1 = Xn */
/* Yn2 = Yn1 */
/* Yn1 = acc */
/* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
/* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
#ifndef ARM_MATH_BIG_ENDIAN
state_in = __PKHBT(in >> 16, state_in, 16);
state_out = __PKHBT(out, state_out, 16);
#else
state_in = __PKHBT(state_in >> 16, in, 16);
state_out = __PKHBT(state_out >> 16, out, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Decrement the loop counter */
sample--;
}
/* If the blockSize is not a multiple of 2, compute any remaining output samples here.
** No loop unrolling is used. */
if((blockSize & 0x1u) != 0u)
{
/* Read the input */
in = *pIn++;
/* out = b0 * x[n] + 0 * 0 */
#ifndef ARM_MATH_BIG_ENDIAN
out = __SMUAD(b0, in);
#else
out = __SMUADX(b0, in);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* acc = b1 * x[n-1] + b2 * x[n-2] + out */
acc = __SMLALD(b1, state_in, out);
/* acc += a1 * y[n-1] + a2 * y[n-2] */
acc = __SMLALD(a1, state_out, acc);
/* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
/* Calc lower part of acc */
acc_l = acc & 0xffffffff;
/* Calc upper part of acc */
acc_h = (acc >> 32) & 0xffffffff;
/* Apply shift for lower part of acc and upper part of acc */
out = (uint32_t) acc_l >> lShift | acc_h << uShift;
out = __SSAT(out, 16);
/* Store the output in the destination buffer. */
*pOut++ = (q15_t) out;
/* Every time after the output is computed state should be updated. */
/* The states should be updated as: */
/* Xn2 = Xn1 */
/* Xn1 = Xn */
/* Yn2 = Yn1 */
/* Yn1 = acc */
/* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
/* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
#ifndef ARM_MATH_BIG_ENDIAN
state_in = __PKHBT(in, state_in, 16);
state_out = __PKHBT(out, state_out, 16);
#else
state_in = __PKHBT(state_in >> 16, in, 16);
state_out = __PKHBT(state_out >> 16, out, 16);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
}
/* The first stage goes from the input wire to the output wire. */
/* Subsequent numStages occur in-place in the output wire */
pIn = pDst;
/* Reset the output pointer */
pOut = pDst;
/* Store the updated state variables back into the state array */
*__SIMD32(pState)++ = state_in;
*__SIMD32(pState)++ = state_out;
/* Decrement the loop counter */
stage--;
} while(stage > 0u);
#else
/* Run the below code for Cortex-M0 */
q15_t *pIn = pSrc; /* Source pointer */
q15_t *pOut = pDst; /* Destination pointer */
q15_t b0, b1, b2, a1, a2; /* Filter coefficients */
q15_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
q15_t Xn; /* temporary input */
q63_t acc; /* Accumulator */
int32_t shift = (15 - (int32_t) S->postShift); /* Post shift */
q15_t *pState = S->pState; /* State pointer */
q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
uint32_t sample, stage = (uint32_t) S->numStages; /* Stage loop counter */
do
{
/* Reading the coefficients */
b0 = *pCoeffs++;
pCoeffs++; // skip the 0 coefficient
b1 = *pCoeffs++;
b2 = *pCoeffs++;
a1 = *pCoeffs++;
a2 = *pCoeffs++;
/* Reading the state values */
Xn1 = pState[0];
Xn2 = pState[1];
Yn1 = pState[2];
Yn2 = pState[3];
/* The variables acc holds the output value that is computed:
* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
*/
sample = blockSize;
while(sample > 0u)
{
/* Read the input */
Xn = *pIn++;
/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
/* acc = b0 * x[n] */
acc = (q31_t) b0 *Xn;
/* acc += b1 * x[n-1] */
acc += (q31_t) b1 *Xn1;
/* acc += b[2] * x[n-2] */
acc += (q31_t) b2 *Xn2;
/* acc += a1 * y[n-1] */
acc += (q31_t) a1 *Yn1;
/* acc += a2 * y[n-2] */
acc += (q31_t) a2 *Yn2;
/* The result is converted to 1.31 */
acc = __SSAT((acc >> shift), 16);
/* Every time after the output is computed state should be updated. */
/* The states should be updated as: */
/* Xn2 = Xn1 */
/* Xn1 = Xn */
/* Yn2 = Yn1 */
/* Yn1 = acc */
Xn2 = Xn1;
Xn1 = Xn;
Yn2 = Yn1;
Yn1 = (q15_t) acc;
/* Store the output in the destination buffer. */
*pOut++ = (q15_t) acc;
/* decrement the loop counter */
sample--;
}
/* The first stage goes from the input buffer to the output buffer. */
/* Subsequent stages occur in-place in the output buffer */
pIn = pDst;
/* Reset to destination pointer */
pOut = pDst;
/* Store the updated state variables back into the pState array */
*pState++ = Xn1;
*pState++ = Xn2;
*pState++ = Yn1;
*pState++ = Yn2;
} while(--stage);
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
}
/**
* @} end of BiquadCascadeDF1 group
*/
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